Two Pakistani brothers accused of a plotting a terrorist attack entered not guilty pleas in Fort Lauderdale federal court on Friday. The Oakland Park pair face charges accusing them of conspiring to deploy explosive weapons against an American target.

The brothers, 20-year-old Raees Alam Qazi and 30-year-old Sheheryar Alam Qazi, have each been charged in an indictment with one count of conspiracy to use a weapon of mass destruction and one count of conspiracy to provide material support to terrorists.

The brothers were arrested last week by the FBI and remain in custody at the Broward County Jail. Prosecutors said the Qazi brothers were born in Pakistan, but are both naturalized U.S. citizens.

Federal authorities would disclose few details of the ongoing investigation, but said the alleged plot was “disrupted.” They declined to comment on the weapon type, the target, the terrorism organization or the alleged plot.

Authorities said the indictment was not the result of a sting operation.

Given the nature of the charges, it is likely the defendants won’t be eligible for a bond before trial. The brothers and their attorneys, Daniel Ecarius and Ronald Chapman, may choose not to challenge their detention. Ecarius, who represents Raees Alam Qazi, did not return a call for comment; Chapman declined to reveal his strategy.

Meanwhile, Assistant U.S. Attorney Karen Gilbert disclosed in court papers that the case was built on U.S. government surveillance of the brothers’ phones, including presumably their conversations with foreign contacts. The evidence was obtained under the Foreign Intelligence Surveillance Act, a law that has been strengthened in the post-9/11 era for prosecution of terrorism cases.

Prosecutors said that starting in July 2011, the brothers conspired to provide transportation, money, lodging and other aid toward a plan to use a large-scale weapon somewhere in the United States.

“Any potential threat posed by these two individuals has been disrupted, " Wifredo Ferrer, the U.S. attorney for the Southern District of Florida, said in a statement issued last Friday. “Since September 11, 2001, the top priority of the Department of Justice and this U.S. Attorney’s Office has been to deter and prosecute acts of terrorism.”

The case is being investigated by the FBI’s South Florida Joint Terrorism Task Force.

If convicted, the Qazis each face a sentence of up to 15 years in prison on the material support charge, and a potential life sentence on the weapon of mass destruction charge.